Re: fusors drives agility and stufflikethat

     Arrgh!  I can't stand it anymore.  I was trying to be good,
trying to keep quiet, but I just HAVE to say something about fusion
and agility.  Behold two Gazoid comments:


AGILITY

     At first glance it would appear that Agility and Acceleration
are unrelated.  Yes indeedy do.  After all, one is the ability to
rotate the ship, while the other is the ability to accelerate in a
straight line.  Starships lack the tires, wheels, fins, wings, flippers,
or any of the other things which force terrestrial, aquatic, atmospheric,
or waddling vehicles to make trade-offs between agility and acceleration,
so these qualities should be independant.
     Or should they?  SOME mechanism is required to rotate the ship.  It
might be attitude jets, momentum wheels, thrust deflection, or even a
team of trained Psionics with the Vertigo power, but it has to be there.
And the moment of inertia of a starship, even a puny Scout, is
considerable -- 100 tonnes, 30 meters long, you don't rotate something
like that just by kicking.  Unless you are Very Big.  In which case you
probably don't need a starship.
     In fact, to really whip a starship around (like in a few seconds or
so) the attitude jets have to produce a significant fraction of a 'g'.
And that kind of acceleration does not come cheap.  Really.  Honest.
Would I lie?


FUSION DRIVES

     Everyone seems to have had a fine and dandy time calculating the
specific impulses for various fusion reactions.  This is tonnes of fun,
good clean sport, and provides hours of opperating pleasure.  It also
omits one Important Consideration:

     Why assume that the drives are 100% efficient?

     There is no reason to assume that fusion drives will be 100%
efficient.  In fact, there is good hard experimental evidence to the
contrary.  I have read in non-classified sources that modern
thermonuclear bombs are only 10% efficient.  My own crude estimates,
also based on non-classified sources (I am, after all, a non-
classified kinda guy) tend to confirm this.
     Consider the implications:  Drives must meet demanding requirements.
They must opperate for hours, channel all their thrust in one direction,
and protect their opperators from heat, shock, and radiation.  Bombs do
not need to meet any of these requirements.  In fact, it is the function
of bombs not to meet these requirements.  It is part of the very nature
of bombs that they FAIL a single one of these requirements, and do so
in as spectacular a fashion as possible.
     If such a simple device as a thermonuclear bomb can only achieve
10% efficiency, it is reasonable to suppose that thermonuclear reaction
drives will be far worse, in the vicnicity of 1% efficiency, which works
out to an exhaust velocity of 100 km/sec or thereabouts, which, oddly
enough, is about the exhaust velocity of Eight Worlds ships.



SPECIAL BONUS GAZOID COMMENT: FUSORS

     After a lot 'o diddling, I came to the conclusion that fusors and
drives had to meet such a strikingly different set of requirements
that I could not believe they would be in any way related.  So it
is in the Eight Worlds.  Drives are open ended linear pinch devices,
much like the late unlamented Tandem Mirror machine at Livermore,
and burn D + D --> T + p or He3 + n in vast quantities.  Fusors are
small high-field devices like the Altocampus machine at MIT, and
burn p + Li6 --> He3 + He4  ('To dream, the impossible dream...').
Since the products of this reaction are both ionized, they can be
run thrugh an MHD generator to produce power without any of the
nasty bad neutrons associated with less sexy reactions.
     I have, of course, made a complete table of specific powers,
specific impulses, efficiencies, and whatnot, but its at home, I
am not, and I haven't looked at it for five years anyway.  If
anyone is really interested, I can dredge it out (dredge dredge).


Cap'n Paul


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